If you've had any networking problems on the 360, done a network test then pressed Y for detailed status, you've seen a dialog like this (this one's not mine; thanks google image search):

What do all these codes mean? I don't think Microsoft tech support will tell us, perhaps for job security reasons.
I can guess some of them:

T = network Type (wired / wireless)

A = private Address / subnet mask

G = Gateway

D = DNS1 / DNS2

N = wireless access point Name (SSID)

S = wireless Security type

What about W, X, Y, Z, ID, L, Q and C? I think Q might be the error code, and MS does have an error code search page, but the explanation for code 80070435 (with I've had with a wired connection) is hopelessly uninformative.